Organizers of the growing movement to persuade investors to divest from fossil fuels will announce a major milestone Monday, when more than 50 foundations, institutions and wealthy individuals who control at least $50 billion in assets will pledge to begin pulling their investments from fossil fuels, particularly coal and oil.

The announcement, a day after more than 300,000 climate activists descended on New York City for an unprecedented People’s Climate March, is the latest sign that divestment is gaining steam. One of the foundations pledging to divest is the Rockefeller Brothers Fund, created by the descendents of Standard Oil co-founder John D. Rockefeller; one of the institutions pledging is the World Council on Churches–which represents over 300 churches and 590 million people in 150 countries..

“The snowball is picking up speed very rapidly,” said Ellen Dorsey, executive director of the Wallace Global Fund and the originator of the Divest-Invest initiative. “There’s a new urgency imposed by the science. We have to orchestrate the end of the fossil fuel era in a very short time frame.”

Archbishop Desmond Tutu, a global figure in the decades-long fight against apartheid in South Africa and winner of the Nobel Peace Prize, videotaped a message urging “individuals and institutions of conscience” to act on climate change. The message will be aired during the press conference.

The Goldman Environmental Foundation, based in San Francisco, as well as the John and Marcia Goldman Foundation, are among the Bay Area foundations announcing plans to divest Monday.

“We are really interested in not just divesting from coal and oil, but investing in clean energy and climate solutions moving forward,” said David Gordon, executive director of the Goldman Environmental Foundation. “Foundations are starting to walk the walk. We need to back up what we believe in with our financial assets.”

Divesting is a complex process. Foundations typically spend months researching and deliberating the decision, which requires looking at existing holdings, examining the foundation’s core mission and thinking about long-term risks and investment goals.

Each foundation will pursue its own divestment strategy on its own timetable, but the goal is to complete the process within five years. The Rockefeller Brothers fund has pledged to divest from coal and tar sands, but has not made a decision on natural gas.

The “Go Fossil Free” movement, driven by growing alarm over the impact of fossil fuels on climate change, is the latest iteration of what’s known as “socially responsible investing,” in which individuals and institutions examine their portfolios for companies whose businesses offend their political or ethical views, whether it’s gun makers, tobacco companies or, in this case, businesses involved in the petroleum industry.

In May, Stanford University’s Board of Trustees announced that Stanford, which has a $19 billion endowment, would no longer invest in 100 publicly traded companies that are focused on coal mining and extraction.

“Stanford’s decision was extremely significant,” said Dorsey. “This issue is being hotly debated in Silicon Valley. There’s been exponential growth in this movement in a very short period of time.”

A transit village with apartments, retailers, restaurants and a hotel is rising in Milpitas next to The Great Mall, close to light rail and the under-construction BART station. It’s one of several Silicon Valley projects sprouting up near transit.

Snapchat has managed to build something lasting out of photos that vanished almost instantly. The fast-growing social network for millennials has come a long way since its founder Evan Spiegel dropped out of Stanford University in 2012, three classes shy of graduation.